What is the minimum water supply duration required for most sprinkler systems?

The minimum water supply duration required for most sprinkler systems as specified in NFPA 13 is generally 30 minutes. This duration is established to ensure that during a fire event, the sprinkler system can function effectively for a sufficient period of time to control or suppress the fire until additional firefighting resources arrive.

A 30-minute supply is considered a practical balance that allows for effective activation of the sprinkler system, providing an adequate response time during the critical early stages of a fire. This period takes into account that fires can escalate quickly, and having a reliable water supply allows the system to deliver consistent extinguishing efforts.

In some specific scenarios or types of occupancies, longer durations may be required, but the standard guideline for most systems is 30 minutes, thus making it the ideal choice for this question.